Collapsible ladder assembly

ABSTRACT

A collapsible ladder assembly having a ladder for use alternatively by itself or in combination with a carrying case in which said ladder is formed from a plurality of swingably interconnected scissored sections movable between a collapsed position in which they overlap each other and a fully extended position in which they are in a generally end to end relationship. The case is movable between a closed position for housing the collapsed ladder and an open position in which it can be connected to the fully extended ladder for supporting it in a generally upright position or disposed over the partially extended ladder to form an elevated platform therewith.

United States Patent Forestal et al.

[54] COLLAPSIBLE LADDER ASSEMBLY. A

[72] Inventors: Robert J, Forestal; Jack W. Hanley,

both of Indianapolis, Ind.

[73] Assignee: Forestal Enterprises, Indianapolis,

Ind.

[22] Filed: May 28, 1971 [21] Appl. No.1 148,031

[52] US. Cl. ..182/22, 182/28, 182/129, 182/151 [51] Int. Cl. ..E06c 1/383 [58] Field of Search ..182/28, 20, 21, 22, 157, 27, 182/129, 151

2/l893 Stibbs ..182/157 [451 Oct. 3, 1972 846,087 5/1907 Bradt ..182/15 1 2,749,009 6/1956 Price ..182/157 Primary Examiner-Reinaldo P. Machado Attorney-Trask, Jenkins & Hanley [57] v ABSTRACT A collapsible ladder assembly having a ladder for use alternatively by itself or in combination with a carrying case in which said ladder is formed from a plurality of swingably interconnected scissored sections movable between a collapsed position in which they overlap each other and a fully extended position in which they are in a generally end to end relationship. The case is movable between a closed position for housing the collapsed ladder and an open position in which it can be connected to the fully extended ladder for supporting it in a generally uprightposition or disposed over the partially extended ladder to form an elevated platform therewith.

l2 Claims, l2 Drawing Figures PATENTEDflm I972 sum 1 OF 3 IN TOR ROBERT J. RE L 5 TTORNEY JCK W. HANL PATENTEDnm 3 I972 iil SHEET 2 [1F 3 m T "QM I2 3 c. foo F a INVENTOR ROBERT J. FORESTAL JACK W. HANLEY ATTORNEYS PATENTEllpma 1972 I 3,695,389

sum 3 OF 3 INVENTOR ROBERT J. FORESTAL JACK W. HANLEY ATTORNEYS BACKGROUND OF INVENTION Collapsible ladders have long been known in the art. Such ladders, however, if they have an appreciable height, are not able to be collapsed into compact size such that they can be easily carried through narrow doorways, onto elevators, and the like. Further, if they are used in forming an elevated platform, it generally requires two such ladders to form the supports for the platform, which platform is generally formed from a number of elongated planks or rigid sheets. Again, the size of such structures makes it difficult to. carry or maneuver them in small areas.

The instant invention overcomes these problems and disadvantages by providing a ladder which can be adjusted between an extended position in which it has an appreciable height and a compact collapsed position in which it can be carried and stored in a carrying case, which case also provides a means for supporting the ladder in extended position and a platform supported on said ladder.

SUMMARY OF THE INVENTION In accordance with one form of the invention, there is provided a collapsible ladder formed from a plurality of pairsof first legs and a plurality of pairs of second legs disposed laterally inwardly of said first legs with each pair of said'second legs being disposed within the longitudinal extent'of a pair of said first legs and having their ends overlapping the adjacent ends of adjacent pairs of said first legs. The aligned pairs of first and second legs are swingably interconnected intermediate their lengths by a first set of rungs, and the overlapping ends of said pairs of first and second legs are swingably interconnected by a second set of rungs. In this manner, said legs and rungs form a plurality of scissored ladder sections which are movable between a collapsed position with said pairs of first and second legs respectively overlapping adjacent pairs of said first and second legs and a fully extended position with said pairs of first and second legs respectively in a generally end to end relationship with adjacent pairs of said first and second legs.

Said ladder in its collapsed position is received in a carrying case comprising a pair of swingably connected shells each having a back wall and a plurality of interconnected side walls. The shells are movable between a closed position in which the back walls are in opposed confronting relationship and an open position in which said back walls are coplanar. With the case in said open position and the ladder in a partially extended position in which a plurality of the ends of said first and second legs are in engagement with the ground, said case is received over the ladder with its back walls resting on the ends of said legs opposite the plurality of groundengaging leg ends whereby said case forms a platform on said ladder. With the case in its open position and the ladder fully extended, they can be disposed in an angular relationship whereby said case supports said ladder in a generally upright step ladder-forming position.

A plurality of ribs project inwardly from the case back walls to engage a plurality of the ladder rungs for supporting the collapsed ladder in the case and a plurality of said rungs when the ladder and case are in their platform-forming positions for thus distributing the weight of a load applied to the case. Pairs of links and arms are also swingably mounted on the case for engagement with ladder rungs for interconnecting the case and fully extended ladder when they are in their step ladder-forming position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 6 is a transverse section taken on line 6-6 of FIG. 5;

FIG. 7 is a perspective view of the ladder shown in FIG. 2, but showing said ladder in fully extended position; I

FIG. 8 is a side elevation of the ladder assembly shown in FIG. 2, but showing said assembly in a partially extended platform-forming position;

FIG. 9 is a side elevation similar to FIG. 8, but showing said assembly in another platform-forming position;

FIG. 10 is an enlarged transverse section taken on line 10-10 of FIG. 8;

FIG. 11 is an enlarged transverse section taken on line 11-11 ofFIG. 8; and

FIG. 12 is a side elevation of the ladder assembly shown in FIG. 2, but showing said assembly in a step ladder-forming position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT and carried in a case 12 and various extended positions of adjustment in which it can be used alone as shown in FIG. 7 and in various combinations with said case to provide platform structures as shown in FIGS. 8 and 9 and a step ladder as shown in FIG. 12.

As best illustrated in FIG. 7, the ladder comprises a plurality of pairs of laterally spaced first legs 14, 15 and 16. A plurality of pairs of second legs 17, 18 and 19 are disposed laterally inside the legs 14-16. As shown, the pairs of legs 17, 18 and 19 are disposed within the longitudinal extent of the pairs of legs 14, 15 and 16, respectively, with the ends of each of the legs 17-19 overlapping the adjacent ends of adjacent legs 14-16. Each of the pairs of aligned legs 14 and 17, 15 and 18, and 16 and 19 are swingably interconnected intermediate their lengths by transverse rungs 20. Each of the overlapping ends of the pairs of legs are swingably interconnected by transverse rungs 22 set slightly inwardly from said leg ends. And conveniently, the outer ends of the pairs of legs 14, 17, 16 and 19 are interconnected by transverse rungs 23.

Thus, the several pairs of legs form a plurality of swingably interconnected scissored sections which are movable into a compact completely collapsed position as shown in FIGS. 2 and 3 in which adjacent pairs of the legs 14-16 overlap each other in abutting relation with the adjacent pairs of legs 17-12 in a like overlapping abutting relation. The ladder can be moved into partially extended positions as shown in FIGS. 8 and 9 in which the scissored sections are longitudinally spread apart to provide various angles between the pairs of legs 14 and 17, 15 and 18, and 16 and 19. And as shown in FIG. 7, the ladder is movable into a fully extended position in which there is a very small angle between the pairs of legs 14 and 17, 1S and 18, and 16 and 19. In such a fully extended position, the inner legs are in substantial end to end relationship, as are the outer legs. The ends of the inner pairs of legs 17-19, however, overlap and abut the adjacent ends of adjacent pairs of said inner legs, and in a like manner, the ends of the outer pairs of legs 14-16 overlap and abut the adjacent ends of adjacent pairs of said outer legs. This prevents the legs in each scissored section from swinging through center and thus forms a rigid structure so that the ladder in the position shown in FIG. 7 can be leaned against any desired wall structure and climbed by a user placing his feet on the various rungs 20 and 22. Normally, the rungs 23, which primarily serve as cross-braces, are not used in such climbing since they lie immediately adjacent the ends of the ladder.

As shown in FIGS. 2 and 3, the case 10 comprises a pair of opposed shells 24 and 25, each of which is identical in its construction. Thus, each of said shells comprises a back wall 26 interconnected to opposed pairs of side walls 27 and 28. As shown in FIG. 2, the walls 27 at one end of the case are swingably interconnected by a plurality of hinges 30 recessed in said walls whereby said case is movable between its closed position as shown in FIG. 2 with the back walls 26 in opposed confronting relationship and a fully open position as shown in FIG. 9 in which the back walls .26 of the shells 24 and are in a continuous coplanar relationship. Conveniently, a latch 32 is mounted on the side wall 27 of shell 25 opposite the hinge for engagement with a keeper 33 on the adjacent side wall 27 of shell 24 for thus releasably locking the case in its closed position. A carrying handle 34 is also mounted on shell 24.

For reasons that will become more apparent hereinafter, the case is releasably lockable in its fully open position. To this end, a guide 36 is mounted on each of the side walls 28 of shell 25 adjacent the hinged side wall 27. A slide 38 is carried in each of the guides 36 and is provided with a handle 39 projecting outwardly through an elongated slot 411 formed in the guide 36. The slides 38 are receivable in channels 42 mounted on the side walls 28 of shell 24 adjacent the hinged walls 27 of said shell. As shown in FIG. 9, with the shells 24 and 25 in their fully open position, the guides and channels 36 and 42 are disposed in longitudinal alignment so that the slides 38 can be easily moved into and out of their locking positions in said channels.

As shown in FIGS. 2 and 3, a plurality of laterally spaced stiffening ribs 48 project inwardly from each of the back walls 26 in parallelism with the side walls 28. As shown, with the ladder in its collapsed position in the closed case, said ribs abut the rungs 23. Thus, with all of the ladder legs 14-19 abutting the shell side walls and all but legs 15 and 113 abutting the back walls 26, the ladder will be supported against relative movement in the case.

As shown in FIG. 8, the ladder can be partially extended into a position in which the scissored sections formed by the pairs of legs 14 and 17, 15 and 18, and 16 and 19 are spread slightly apart with the distance between the outer ends of the legs 14 and 19 approximating the length of one of the shells 24 or 25. With the ladder so extended, it is placed on the ground with one end of each of the legs 14-19 supported on the ground. The case is opened and one of the shells (24 in FIG. 8) is placed over the upper ends of the legs 14-19. In such position, the scissored leg sections are supported against further extension by the outer upper ends of the legs 14 and 19 engaging the back wall 26 at its juncture with the side walls 27. In such position, the ribs 48 on the back wall 26 will abut a pair of the rungs 22 and a pair of the rungs 20 for distributing a load applied to the then upwardly presented face of the back wall 26. Thus, the assembly in the position shown in FIG. 8 provides an elevated platform with the ribs 48 distributing the weight of the load applied thereto.

The assembly in the position shown in FIG. 8 provides a platform having a cross-sectional extent equal to that of one of the shells 24 or 25. In order to provide a platform having a cross-sectional extent equal to the combined cross-sectional extents of the shells 24 and 25, the case and ladder are moved into the position shown in FIG. 9. In such position, the ladder sections are again extended, but they are extended to an extent such that the distance between the opposed ends of the legs 14 and 19 is equal to the distance between the remote side walls 27 of the fully opened case 10. Again, the scissored ladder sections are placed on the ground with one end of the legs 14-19 resting on the ground and the opposite or upper ends of said legs being received against the back walls 26 of the case shells 24 and 25. With the ladder and case in the orientation shown in FIG. 9, the ladder will be releasably retained in its partially extended position by the opposed upwardly oriented ends of the legs 14 and 19 engaging the back walls 26 of the shells at their junctures with the end walls 27 remote from the hinge 30. Like in the orientation shown in FIG. 8, the weight of the load applied to the platform will be distributed to the ladder by the ribs 48 on the shell back walls engaging upwardly disposed rungs 22 and 20. In order to relieve stress on the hinge 30, the slides 38 are extended into the channels 42 so that said slides and their associated guides and channels absorb the load applied to the platform at the hinged juncture of the opened shells 24 and 25.

The ladder and case may also be interconnected to provide the step ladder configuration as illustrated in FIG. 10. To assembly them into such an orientation, the ladder 10 is moved into its fully extended position, and the case 12 is moved into its fully open position in which the shell back walls 26 are in a continuous coplanar relationship. In order to prevent accidental closing of the case, the slides 33 are extended into their cooperating channels 42. The fully open case and extended ladder are then disposed in an upwardly projlegting angularly disposed relationship as shown in FIG. The case and ladder are releasably retained in their angularly disposed relationship by a pair of links 55 which are swingable outwardly from the shell 25. As shown in FIG. 3, each of the links 55 is swingably interconnected, as by a pivot pin 56 adjacent one of its ends, to a pair of adjacent ribs 48. The opposite end of each of said links is provided with a notch 58 adapted to be received over one of the ladder rungs 20. Desirably, the links 55 are frictionally retained between the pairs of ribs 48 to which they are swingably connected to prevent their accidentally swinging outwardly from the shell 25 when they are not in use.

As shown in FIGS. 5 and 6, a pair of arms 60 are swingably connected, as by pins 62, to the side wall 27 of the shell 25 remote from the hinge 30 on said shell. Each of the arms 60 has a pair of angularly disposed ribs 64 projecting outwardly therefrom. The arms 60 are swingable outwardly aboutthe axes of the pins 62 to project toward the ladder whereby the pairs of ribs 64 are receivable over one of the rungs 22. Thus, the case and ladder are interconnected by the links 55 and arms 60 to releasably maintain the assembly in a step ladder-forming configuration. As shown in FIG. 6, each of the arms 60 is releasably retained in its retracted position within the extent of shell 25 by a detent 65 formed on the face of the arm opposite the ribs 64 and bindingly retained in a recess 67 in the end wall 27 of shell 25. The arms are set laterally inwardly from the shell side walls 28 sufficiently to clear the inner pairs of ladder legs 1 7-19 when the ladder is in its collapsed position in the case and project inwardly from their associated shell side wall 27 a distance less than the spacing between the ladder rungs 22 and 23 and the ends of the ladder legs to which said rungs are connected.

While the ladder has been described herein as employing three scissored sections, it is to be understood that said ladder may employ any desired numbers of such sections.

We claim:

1. A collapsible ladder assembly having a ladder for use alternatively by itself or in combination with a carrying case and comprising a plurality of pairs of laterally spaced first legs, a plurality of pairs of second legs disposed laterally inwardly of said first legs, each pair of said second legs being disposed within the iongitudinal extent of a pair of said first legs with their ends overlapping the adjacent ends of adjacent pairs of said first legs, a set of first rungs swingably interconnecting each of the pairs of aligned first and second legs, a setof second rungs swingably interconnecting i the overlapping ends of said first and second legs, said ladder being movable between a fully collapsed position with said pairs of first and second legs respectively overlapping adjacent pairs of first and second legs and a fully extended position with said pairs of first and second legs respectively in substantial end to end relationship with adjacent pairs of first and second legs, said case having a pair of opposed interconnected shells movable between a closed ladder-carrying position and an open ladder-supporting position, and means on said shells for supporting said ladder in extended positions of adjustment when said shells are in said open ladder-supporting position.

2. A collapsible ladder assembly as set forth in claim 1 in which each of said shells comprises a back wall interconnected to a plurality of side walls, said back and side walls comprising said means whereby said back and side walls will engage a plurality of the ends of said first and second legs when said legs are swung into a partially extended position in which the ends opposite said plurality of ends are in engagement with the ground with said back walls forming a platform extending over said ladder.

3. A collapsible ladder assembly as set forth in claim 2 with the addition that a set of third rungs interconnects the pairs of first and second legs at the ends of the ladder, and a plurality of laterally spaced ribs extend inwardly from each of Said back walls, said ribs being engageable with a plurality of said second and third sets of rungs when said ladder is in said partially extended position and said back walls form said platform, and with said second set of rungs when said ladder is collapsed and said case is in closed position.

4. A collapsible ladder assembly as set forth in claim 2 with the addition that means are mounted on said shells for releasably locking them in an open position in which their back walls are coplanar.

5. A collapsible ladder assembly as set forth in claim 4 in which said means comprises a pair of channels mounted on one of said shells, a pair of guides mounted on the other of said shells in alignment with said channels when said back walls are coplanar, and a slide carried in each of said guides and movable into one of said channels.

6. A collapsible ladder assembly as set forth in claim 2 with the addition that a set of third rungs interconnects the pairs of first and second legs at the ends of the ladder, a plurality of laterally spaced ribs extend inwardly from each of said back walls, said ribs being engageable with a plurality of said second and third sets of rungs when said ladder is in said partially extended position and said back walls form said platform, and with said second set of rungs when said ladder is collapsed and said case is in closed position, and means are mounted on said shells for releasably locking them in an open position in which their back walls are coplanar.

7. A collapsible ladder assembly as set forth in claim 1 in which said shells are movable into a coplanar open position, means are mounted on said shells for releasably locking them in said coplanar open position, and said means comprises a plurality of members swingably mounted on one of said shells and adapted to engage a plurality of rungs on said ladder whereby said ladder and case in extended and open position, respectively, can be angularly disposed with respect to each other with said members engaging said rungs for supporting said ladder in an angularly disposed upright position.

8. A collapsible ladder assembly as set forth in claim 7 in which said members comprise a pair of links engageable with a rung in said first set of rungs and a pair of arms engageable with a rung in said second set of rungs.

9. A collapsible ladder assembly having a ladder for use alternatively by itself or in combination with a carrying case and comprising a plurality of pairs of laterally spaced first legs, a plurality of pairs of second legs disposed laterally inwardly of said first legs, each pair of said second legs being disposed within the longitudinal extent of a pair. of said first legs with their ends overlapping the adjacent ends of adjacent pairs of said first legs, a set of first rungs swingably interconnecting each of the pairs of aligned first and second legs, a set of second rungs swingably interconnecting the overlapping ends of said first and second legs, said ladder being movable between a fully collapsed position with said pairs of first and second legs respectively overlapping adjacent pairs of first and second legs and a fully extended position with said pairs of first and second legs respectively in substantial end to end relationship with adjacent pairs of first and second legs, said case having a pair of opposed shells each comprising a back wall connected to a plurality of side walls, means swingably interconnecting said shells for movement between a closed position in which their back walls are in opposed confronting relationship and an open position in which their back walls are coplanar, means for releasably locking said case in open position, a plurality of ribs projecting inwardly from each of said side walls engageable with a plurality of said rungs when said ladder is partially extended with the ends of a plurality of said first and second legs in engagement with the ground and the ends opposite said plurality of ends engaging the shell back walls with the case in open position and extending over said ladder, and a plurality of members swingably mounted on one of said shells adapted to engage a plurality of rungs on said ladder whereby said ladder and case in extended and open positions, respectively, can be angularly disposed with respect to each other with said members engaging said rungs for supporting said ladder in an angularly disposed upright position.

10. A collapsible ladder assembly as set forth in claim 9 in which said members comprise a pair of links swingably connected between pairs of said ribs and a pair of arms swingably mounted on one of said side walls.

11. A collapsible ladder assembly as set forth in claim 9 in which said means for releasably locking the case in open position comprises a pair of guides mounted on one of said shells, a pair of guides mounted on the other of said shells in alignment with said channels when said back walls are coplanar, and a slide carried in each of said guides movable into one of said channels.

12. A collapsible ladder assembly as set forth in claim 9 in which said means for releasably locking the case in open position comprises a pair of guides mounted on one of said shells, a pair of guides mounted on the other of said shells in alignment with said channels when said back walls are coplanar, and a slide carried in each of said guides movable into one of said channels, and said members comprise a pair of links swingably connected between pairs of said ribs and a pair of arms swingably mounted on one of said side walls. 

1. A collapsible ladder assembly having a ladder for use alternatively by itself or in combination with a carrying case and comprising a plurality of pairs of laterally spaced first legs, a plurality of pairs of second legs disposed laterally inwardly of said first legs, each pair of said second legs being disposed within the longitudinal extent of a pair of said first legs with their ends overlapping the adjacent ends of adjacent pairs of said first legs, a set of first rungs swingably interconnecting each of the pairs of aligned first and second legs, a set of second rungs swingably interconnecting the overlapping ends of said first and second legs, said ladder being movable between a fully collapsed position with said pairs of first and second legs respectively overlapping adjacent pairs of first and second legs and a fully extended position with said pairs of first and second legs respectively in substantial end to end relationship with adjacent pairs of first and second legs, said case having a pair of opposed interconnected shells movable between a closed ladder-carrying position and an open laddersupporting position, and means on said shells for supporting said ladder in extended positions of adjustment when said shells are in said open ladder-supporting position.
 2. A collapsible ladder assembly as set forth in claim 1 in which each of said shells comprises a back wall interconnected to a plurality of side walls, said back and side walls comprising said means whereby said back and side walls will engage a plurality of the ends of said first and second legs when said legs are swung into a partially extended position in which the ends opposite said plurality of ends are in engagement with the ground with said back walls forming a platform extending over said ladder.
 3. A collapsible ladder assembly as set forth in claim 2 with the addition that a set of third rungs interconnects the pairs of first and second legs at the ends of the ladder, and a plurality of laterally spaced ribs extend inwardly from each of said back walls, said ribs being engageable with a plurality of said second and third sets of rungs when said ladder is in said partially extended position and said back walls form said platform, and with said second set of rungs when said ladder is collapsed and said case is in closed position.
 4. A collapsible ladder assembly as set forth in claim 2 with the addition that means are mounted on said shells for releasably locking them in an open position in which their back walls are coplanar.
 5. A collapsible ladder assembly as set forth in claim 4 in which said means comprises a pair of channels mounted on one of said shells, a pair of guides mounted on the other of said shells in alignment with said channels when said back walls are coplanar, and a slide carried in each of said guides and movable into one of said channels.
 6. A collapsible ladder assembly as set forth in claim 2 with the addition that a set of third rungs interconnects the pairs of first and second legs at the ends of the ladder, a plurality of laterally spaced ribs extend inwardly from each of said back walls, said ribs being engageable with a plurality of said second and third sets of rungs when said ladder is in said partially extended position and said back walls form said platform, and with said second set of rungs when said ladder is collapsed and said case is in closed position, and means are mounted on said shells for releasably locking them in an open position in which their back walls are coplanar.
 7. A collapsible ladder assembly as set forth in claim 1 in which said shells are movable into a coplanar open position, means are mounted on said shells for releasably locking them in said coplanar open position, and said means comprises a plurality of members swingably mounted on one of said shells and adapted to engage a plurality of rungs on said ladder whereby said ladder and case in extended and open position, respectively, can be angularly disposed with respect to each other with said members engaging said rungs for supporting said ladder in an angularly disposed upright position.
 8. A collapsible ladder assembly as set forth in claim 7 in which said members comprise a pair of links engageable with a rung in said first set of rungs and a pair of arms engageable with a rung in said second set of rungs.
 9. A collapsible ladder assembly having a ladder for use alternatively by itself or in combination with a carrying case and comprising a plurality of pairs of laterally spaced first legs, a plurality of pairs of second legs disposed laterally inwardly of said first legs, each pair of said second legs being disposed within the longitudinal extent of a pair of said first legs with their ends overlapping the adjacent ends of adjacent pairs of said first legs, a set of first rungs swingably interconnecting each of the pairs of aligned first and second legs, a set of second rungs swingably interconnecting the overlapping ends of said first and second legs, said ladder being movable between a fully collapsed position with said pairs of first and second legs respectively overlapping adjacent pairs of first and second legs and a fully extended position with said pairs of first and second legs respectively in substantial end to end relationship with adjacent pairs of first and second legs, said case having a pair of opposed shells each comprising a back wall connected to a plurality of side walls, means swingably interconnecting said shells for movement between a closed position in which their back walls are in opposed confronting relationship and an open position in which their back walls are coplanar, means for releasably locking said case in open position, a plurality of ribs projecting inwardly from each of said side walls engageable with a plurality of said rungs when said ladder is partially extended with the ends of a plurality of said first and second legs in engagement with the ground and the ends opposite said plurality of ends engaging the shell back walls with the case in open position and extending over said ladder, and a plurality of members swingably mounted on one of said shells adapted to engage a plurality of rungs on said ladder whereby said ladder and case in extended and open positions, respectively, can be angularly disposed with respect to each other with said members engaging said rungs for supporting said ladder in an angularly disposed upright position.
 10. A collapsible ladder assembly as set forth in claim 9 in which said members comprise a pair of links swingably connected between pairs of said ribs and a pair of arms swingably mounted on one of said side walls.
 11. A collapsible ladder assembly as set forth in claim 9 in which said means for releasably locking the case in open position comprises a pair of guides mounted on one of said shells, a pair of guides mounted on the other of said shells in alignment with said channels when said back walls are coplanar, and a slide carried in each of said guides movable into one of said channels.
 12. A collapsible ladder assembly as set forth in claim 9 in which said means for releasably locking the case in open position comprises a pair of guides mounted on one of said shells, a pair of guides mounted on the other of said shells in alignment with said channels when said back walls are coplanar, and a slide carried in each of said guides movable into one of said channels, and said members comprise a pair of links swingably connected beTween pairs of said ribs and a pair of arms swingably mounted on one of said side walls. 